Fc mu receptor (FcμR)

Fc mu receptor (FcμR) is a transmembrane glycoprotein widely expressed on adaptive immune cells, including B cells, T cells, and to a lesser extent, NK cells in humans (but only on B cells in mice)[3][5]. FcμR selectively recognizes and binds to the Fc portion of IgM antibodies with high affinity, especially when IgM is presented on the same cell surface (*cis* engagement)[3][4][5]. Structurally, FcμR contains a single Ig-like extracellular domain, a transmembrane domain with a conserved histidine, and a cytoplasmic tail with conserved tyrosine and serine residues involved in signaling, although these do not conform to typical ITAM/ITIM motifs found in other Fc receptors[5]. The receptor regulates key aspects of immune tolerance and homeostasis; its dysfunction leads to increased development of autoantibodies and immune dysregulation. While FcμR is not currently a therapeutic drug target, its immune-modulatory roles make it of interest for research in autoimmunity, infection, and B cell biology[3][5].

Other names

TOSOFas apoptotic inhibitory molecule 3 (FAIM3)IGMR (Immunoglobulin M receptor)IgM Fc receptor

Not established clinically. Hypothetically, drugs or biologics could: - Block or modulate IgM binding to FcμR to influence immune signaling - Alter B or T cell responses in autoimmunity or infection by affecting FcμR signaling